title: The ER stress factor XBP1s prevents amyloid-beta neurotoxicity.
abstract: Alzheimer's disease (AD) is an incurable neurodegenerative disorder clinically characterized by progressive cognitive impairment. A prominent pathologic hallmark in the AD brain is the abnormal accumulation of the amyloid-β 1-42 peptide (Aβ), but the exact pathways mediating Aβ neurotoxicity remain enigmatic. Endoplasmic reticulum (ER) stress is induced during AD, and has been indirectly implicated as a mediator of Aβ neurotoxicity. We report here that Aβ activates the ER stress response factor X-box binding protein 1 (XBP1) in transgenic flies and in mammalian cultured neurons, yielding its active form, the transcription factor XBP1s. XBP1s shows neuroprotective activity in two different AD models, flies expressing Aβ and mammalian cultured neurons treated with Aβ oligomers. Trying to identify the mechanisms mediating XBP1s neuroprotection, we found that in PC12 cells treated with Aβ oligomers, XBP1s prevents the accumulation of free calcium (Ca(2+)) in the cytosol. This protective activity can be mediated by the downregulation of a specific isoform of the ryanodine Ca(2+) channel, RyR3. In support of this observation, a mutation in the only ryanodine receptor (RyR) in flies also suppresses Aβ neurotoxicity, indicating the conserved mechanisms between the two AD models. These results underscore the functional relevance of XBP1s in Aβ toxicity, and uncover the potential of XBP1 and RyR as targets for AD therapeutics.
authors.affiliation: Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Sergio
authors.initials: S
authors.lastname: Casas-Tinto
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jonatan
authors.initials: J
authors.lastname: Sanchez-Garcia
authors.forename: Melisa
authors.initials: M
authors.lastname: Gomez-Velazquez
authors.forename: Diego E
authors.initials: DE
authors.lastname: Rincon-Limas
authors.forename: Pedro
authors.initials: P
authors.lastname: Fernandez-Funez
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005123:Eye / Q000473:pathology; D005260:Female; D008297:Male; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D016716:PC12 Cells; D010446:Peptide Fragments / Q000235:genetics* / Q000378:metabolism; D017510:Protein Folding; D012326:RNA Splicing; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D014162:Transfection
chemical_list: D016229:Amyloid beta-Peptides; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D010446:Peptide Fragments; D034741:RNA, Small Interfering; D019837:Ryanodine Receptor Calcium Release Channel; C517798:Xbp1 protein, Drosophila; C075222:amyloid beta-protein (1-42); D002118:Calcium